Association between renal cystic lesions and bilateral Wilms' tumours.

Objectives: Evaluate a potential association between Wilms' tumour (WT) and renal cystic lesions.
Methods: Digital records and imaging files of consecutive patients diagnosed with WT between 2004 and 2014 were retrospectively reviewed under an Institutional Review Board waiver of informed consent. The locations of renal cysts seen on US, CT, and/or MRI were recorded and compared with the locations of newly developed WT.
Results: A total of 48 patients (mean age 3 years 9 months) presented with newly diagnosed WT in the study period. Mean follow-up was 4.5 (range 1-10) years. WT was unilateral in 40 children, bilateral in 8. Renal cysts were identified in only one of the forty patients (2.5 %) with unilateral disease - in the contralateral kidney. In contrast, renal cysts were found in seven of eight patients with bilateral WT (87.5 %), in two of whom, new tumours developed in the same location where cysts had been seen on previous imaging studies.
Conclusions: Renal cystic lesions in patients with Wilms' tumour should be regarded as potential tumour precursors, and followed with frequent imaging.
Key Points: • Cortical renal cystic lesions have a high association with bilateral Wilms' tumour. • In children with Wilms' tumour renal cysts are possible tumour precursors. • MRI appears to be the best modality in depicting the cortical cysts.